Polymers, such as polyurethanes, have many properties that qualify them as high performance polymeric materials, but these polymers still have shortcomings. For example, polyurethanes still suffer from mechanical damage, such as when an object hits a vehicle, it is likely that it will leave a scratch at a minimum. In order to combat mechanical damage, several industries, such as the auto industry, have a need for coatings with high scratch resistance or the ability to self-repair. In addition, several industries have a need for coatings that can self-repair after exposure to ferric ion to minimize corrosion to an object's surface.
Attempts have been made by others to repair mechanical damage to various substrates. One such example includes epoxy matrices containing a glass hollow fiber filled with a monomer and an initiator with the “bleeding” ability to heal polymer networks during crack formation. Another approach utilized a micro-encapsulated dicyclopentadiene monomer in a catalyst embedded polymer matrix, which healed the crack by the ring opening of the monomer. Reversibility of Diels-Alder reactions resulted in another approach to thermally repair damaged areas which utilized maleimide-furan adducts. Mimicking of microvascular structures, water-responsive expandable gels, and formation of supramolecular assemblies are other avenues of remendability. Urban, US 2010/0266784, utilized cyclic oxide-substituted chitosan polyurethane networks for repair of mechanically damaged substrates.
While some progress has been made in attempts to repair damage to various types of systems, coatings still lack the ability to repair mechanical damage to which they are exposed. Thus, a need still exists for polymers that are capable of self repairing mechanical damage to which they are exposed.